CHEMICAL FOAMING OF PVC WITH SURFACE-REACTED CALCIUM CARBONATE (MCC) AND/OR HYDROMAGNESITE

Abstract

The present invention relates to a PVC resin composition for preparing foamed polymer products, to a foamed polymer product prepared from the composition, to a method for preparing a foamed polymer product, to an article comprising the foamed polymer product as well as to the use of a surface-reacted calcium carbonate, hydromagnesite and mixtures thereof for reducing the density of the obtained foamed PVC product.

Claims

1. A PVC resin composition for preparing foamed polymer products, said composition comprising a) at least one PVC resin, b) at least one filler composition in an amount of 0.1 to 75.0 parts per hundred parts of the at least one PVC resin (phr), wherein the at least one filler composition consists of i) 0.5 to 100 parts by weight based on the total dry weight of the at least one filler composition, of a first filler selected from the group consisting of surface-reacted calcium carbonate, hydromagnesite and mixtures thereof, and ii) 0 to 99.5 parts by weight, based on the total dry weight of the at least one filler composition of a second filler selected from the group consisting of ground calcium carbonate, precipitated calcium carbonate and mixtures thereof, wherein the sum of the first filler and the second filler is 100 parts by weight and c) at least one blowing agent in an amount of from 0.10 to 10 phr.

2. The PVC resin composition according to claim 1, wherein the first filler is present in the at least one filler composition in an amount of 1.0 to 90.0 parts by weight, based on the total dry weight of the at least one filler composition and the second filler is present in the at least one filler composition in an amount of 10.0 to 99.0 parts by weight, based on the total dry weight of the at least one filler composition.

3. The PVC resin composition according to claim 1, wherein the at least one filler composition is present in an amount of 1.0 to 60.0 phr.

4. The PVC resin composition according to claim 1, wherein the at least one PVC resin has a K-value of between 50 to 70.

5. The PVC resin composition according to claim 1, wherein the first filler is a surface-reacted calcium carbonate and/or the second filler is a ground calcium carbonate.

6. The PVC resin composition according to claim 1, wherein the first filler has a median particle size d.sub.50 from 1.0 μm to 75 μm, and/or a particle size d.sub.90 from 2.0 to 100 μm, and/or a specific surface area of from 20 to 200 m.sup.2/g as measured by the BET nitrogen method.

7. The PVC resin composition according to claim 1, wherein the second filler has a median particle size d.sub.50 from 0.1 μm to 50 μm, and/or a particle size d.sub.90 from 0.5 to 100 μm, and/or a specific surface area of from 0.1 to 100 m.sup.2/g, as measured by the BET nitrogen method.

8. The PVC resin composition according to claim 1, wherein the first filler and/or the second filler is/are surface-treated with at least one surface treatment agent or is/are a blend of a surface-treated filler and a non-surface treated filler.

9. The PVC resin composition according to claim 1, wherein the at least one blowing agent is present in an amount of between 0.3 phr and 8.0 phr.

10. The PVC resin composition according to claim 1, wherein the at least one blowing agent is a physical blowing agent, an endothermic chemical blowing agent, an exothermic chemical blowing agent or a mixture thereof.

11. The PVC resin composition according to claim 1, wherein the PVC resin composition further comprises at least one component selected from the group comprising nucleating agents, stabilizers, impact modifiers, lubricant additives, processing aids and mixtures thereof.

12. A method for preparing a foamed polymer product comprising the steps of: a) providing a PVC resin composition according to claim 1, and b) subjecting the PVC resin composition of step a) to conditions under which said PVC resin composition is converted into a foamed polymer product.

13. The method according to claim 12, wherein step b) comprises the steps of: b1) feeding the PVC resin composition of step a) into an extruder, b2) exposing the PVC resin composition of step b1) to mechanical force, elevated temperature and/or increased pressure to obtain an at least partially molten PVC resin mixture, b3) passing the at least partially molten PVC resin mixture of step b2) through an extrusion die to form an extrudate, and b4) allowing the extrudate of step b3) to form a foamed polymer product.

14. A foamed polymer product prepared from a PVC resin composition according to claim 1.

15. The foamed polymer product according to claim 14, wherein the foamed polymer product has a density in the range of 0.40 to 1.3 g/cm.sup.3.

16. The foamed polymer product according to claim 14, wherein the foamed polymer product is an open cell PVC foam, a closed cell PVC foam, a foamed rigid PVC sheet or a foamed rigid PVC board.

17. An article comprising the foamed polymer product according to claim 14, wherein the article is a construction material, a window profile, a duct, a pipe, a wall cladding, an insulation material, a sealant, a sign, a printing media, an exhibition board, a crown molding, a door casing, a chair rail, a base board, an automotive part, a marine part or an aircraft part.

18. A method for reducing the density a foamed PVC product, comprising adding a filler selected from the group consisting of surface-reacted calcium carbonate, hydromagnesite, and mixtures thereof, to a foamable PVC resin composition wherein the density of the obtained foamed PVC product is less than a foamed PVC product comprising a filler selected from the group consisting of ground calcium carbonate, precipitated calcium carbonate, and mixtures thereof.

19. The PVC resin composition according to claim 1, wherein the first filler is present in the at least one filler composition in an amount of 10.0 to 40.0 parts by weight, based on the total dry weight of the at least one filler composition, and the second filler is present in the at least one filler composition in an amount of 60.0 to 90.0 parts by weight, based on the total dry weight of the at least one filler composition.

20. The PVC resin composition according to claim 1, wherein the first filler has a median particle size d.sub.50 from 3.6 to 15 μm, and/or a particle size d.sub.90 from 5.0 μm to 25 μm, and/or a specific surface area of from 40 to 90 m.sup.2/g as measured by the BET nitrogen method.

21. The PVC resin composition according to claim 1, wherein the second filler has a median particle size d.sub.50 from 0.7 μm to 7.5 μm, and/or a particle size d.sub.90 from 2.5 μm to 25 μm, and/or a specific surface area of from 2.5 to 20 m.sup.2/g as measured by the BET nitrogen method.

22. The PVC resin composition according to claim 1, wherein the at least one blowing agent is present in an amount of between 0.5 and 6.0 phr.

23. The PVC resin composition according to claim 1, wherein the at least one blowing agent is a mixture of azodicarbonamide and sodium bicarbonate.

24. The foamed polymer product according to claim 14, wherein the foamed polymer product has a density in the range of 0.55 to 0.80 g/cm.sup.3.

Description

EXAMPLES

A. Measuring Methods

[0339] If not otherwise indicated, the parameters mentioned in the present invention are measured according to the measuring methods described below.

Density

[0340] Density measurements are made with Mettler Toledo's Density Kit by using the buoyancy technique. For the determination, 5 samples are cut out of the obtained PVC foams each sample having dimensions of 20×40×10 mm.sup.3 and are weighted in air (M). Subsequently, the buoyancy (P) in distilled water is measured and the density is calculated with the formula (M/(M−P))*density of water.

Foam Bubble Quality Evaluation

[0341] Foamed samples are cut using a “Typ M50 Mikroschnittgerät” to have a clear surface appearance. Following a picture is taken using a microscope with camera and ring light in flat angle position to allow uniform light conditions for the bubble surrounding and enough contrast between the bubbles and the matrix. With a suitable picture interpretation software, the bubbles are counted, and the circumference of each bubble is calculated. Smaller bubble circumferences and higher bubble amounts for the same picture diameters at same enlargement show better nucleation of the foamed polymer.

Weight Median Particle Diameter d.SUB.50 .Value

[0342] Throughout the present invention, d.sub.50 is the weight median particle diameter by weight, for all particulate materials other than surface-reacted calcium carbonate i.e. representing the particle size so that 50 wt.-% of the particles are coarser or finer.

[0343] The weight median particle diameter was measured according to the sedimentation method. The sedimentation method is an analysis of sedimentation behaviour in a gravimetric field. The measurement is made with a Sedigraph™ 5100 of Micromeritics Instrument Corporation. The method and the instrument are known to the skilled person and are commonly used to determine grain size of fillers and pigments. The measurement is carried out in an aqueous solution of 0.1 wt.-% Na.sub.4P.sub.2O.sub.7. The samples were dispersed using a high speed stirrer and supersonic.

Volume Median Particle Diameter d.SUB.50 .Value

[0344] Throughout the present invention, d.sub.50 is the volume median particle diameter by weight for the surface-reacted calcium carbonate, i.e. representing the particle size so that 50 wt.-% of the particles are coarser or finer.

[0345] The volume-based median particle size d.sub.50(vol) and top cut d.sub.90(vol) are evaluated using a Malvern Mastersizer 2000 Laser Diffraction System (Malvern Instruments Plc., Great Britain). The raw data obtained by the measurement is analyzed using the Mie theory, with a particle refractive index of 1.57 and an absorption index of 0.005//using the Fraunhofer theory. The methods and instruments are known to the skilled person and are commonly used to determine particle size distributions; it is, for example, described in “Principles of Instrumental analysis”, seventh edition, Skoog, Holler, Nieman, 2018 (first edition 1992) in Chapter 34 pages 871 to 882, and in many other commonly known reference works.

Specific Surface Area (BET)

[0346] The specific surface area was measured using nitrogen and the BET method according to ISO 9277:2010.

Moisture Content

[0347] Moisture content of the inorganic filler is determined by thermogravimetric analysis (TGA). TGA analytical methods provide information regarding losses of mass with great accuracy, and is common knowledge; it is, for example, described in “Principles of Instrumental analysis”, seventh edition, Skoog, Holler, Nieman, 2018 (first edition 1992) in Chapter 31 pages 820 to 833, and in many other commonly known reference works. In the present invention, thermogravimetric analysis (TGA) is performed using a Mettler Toledo TGA 851 based on a sample of 500+/−50 mg and scanning temperatures from 25° C. to 350° C. at a rate of 20° C./minute under an air flow of 70 ml/min.

[0348] Alternatively, the moisture content of the inorganic filler is determined by the oven method.

K-Value of PVC

[0349] A measure of the molecular weight of PVC based on measurements of viscosity of a PVC solution. It ranges usually between 35 and 80. Low K-values imply low molecular weight (which is easy to process but has inferior properties) and high K-values imply high molecular weight, (which is difficult to process, but has outstanding properties). In general, K-values for a particular PVC resin are provided by the resin producer either on the packaging or the accompanying technical data sheet. The K-values are measured according to ISO 1628-2.

B. Preparation and Testing of Samples

[0350] The components and the respective amounts of the resin compositions prepared in Comparative Examples C1, C2, D1 and D2 and inventive Examples E1 to E3, F1 and F2 are outlined in the following Tables 1 and 2:

TABLE-US-00001 TABLE 1 (The numbers in the table indicate parts per 100 resin (phr)) C1 C2 E1 E2 E3 Example (phr) (phr) (phr) (phr) (phr) PVC K-value 60 100 100 100 100 100 Ca-Zn containing 3.5 3.5 3.5 3.5 3.5 stabilizer Exothermic 0.35 0.35 0.35 0.35 0.35 Foaming agent Endothermic 0.35 0.35 0.35 0.35 0.35 Foaming agent Lubricant 0.05 0.05 0.05 0.05 0.05 processing aid 7 7 7 7 7 Ground natural 25 0 0 22.5 0 CaCO.sub.3 (GCC01) Precipitated 0 0 0 0 22.5 CaCO.sub.3 (PCC01) Modified 0 0 2.5 2.5 2.5 CaCO.sub.3 (SRCC01)

TABLE-US-00002 TABLE 2 (The numbers in the table indicate parts per 100 resin (phr)) D1 D2 F1 F2 Example (phr) (phr) (phr) (phr) PVC K-value 60 100 100 100 100 Ca-Zn containing 3.5 3.5 3.5 3.5 stabilizer Exothermic 0.35 0.35 0.35 0.35 Foaming agent Endothermic 0.35 0.35 0.35 0.35 Foaming agent Lubricant 0.05 0.05 0.05 0.05 processing aid 7 7 7 7 Ground natural 25 0 22.5 0 CaCO.sub.3 (GCC01) Precipitated 0 25 0 22.5 CaCO.sub.3 (PCC01) Hydromagnesite 0 0 2.5 2.5 (HydroMg01)

[0351] In particular, the following commercially available components were used for preparing the compositions:

[0352] Polyvinyl chloride polymer having a K-value of 60 according to ISO 1628-2 (commercially available under the trade name Vynova S6030 PVC; Vynova Wilhelmshaven)

[0353] Ca—Zn-containing stabilizer (commercially available under the trade name Baeropan R9347 PS/7, from Baerlocher, Unterschleissheim).

[0354] Exothermic foaming agent Azodicarbonamide (commercially available under the trade Genitron EPE, from Lanxess, Leverkusen.

[0355] Endothermic foaming agent NaHCO.sub.3 (commercially available under the trade Genitron TP BCH 51051, from Lanxess, Leverkusen).

[0356] Lubricant additive (oxidized PE wax, commercially available under the trade name Baerolube PA Spezial, from Baerlocher, Unterschleissheim).

[0357] Processing aid (acrylic flow modifier, commercially available under the trade name Plastistrength 566 from Arkema, Pierre-Bénite).

[0358] GCC01

[0359] The Ground natural calcium carbonate (GCC) is of natural origin and was prepared according to grinding methods known to the skilled person and as described in U.S. Pat. Nos. 5,533,678 or 5,873,935 with the use of dispersing agents during the wet grinding process and treated with 1 wt % of an industrial fatty acid mixture of C.sub.18/C.sub.16 in amounts of 40 wt %/60 wt %. Such industrial fatty acid mixtures can vary in their C.sub.18/C.sub.16 amount from about 30 wt %-70 wt %/70 wt %-30 wt %, as well as in their carbon chain length being from C.sub.14 to C.sub.20. The obtained GCC has the following characteristics:

[0360] d.sub.90=approximately 0.94 μm;

[0361] d.sub.90=approximately 3.0 μm;

[0362] BET surface area (before surface treatment)=approximately 7.9 m.sup.2/g.

PCC01

[0363] The precipitated calcium carbonate (PCC) is commercially available from Solvay (S.A.) under the trade name Winnofil S Properties and has the following characteristics:

[0364] d.sub.90=approximately 0.1 μm;

[0365] d.sub.90=approximately 0.3 μm;

[0366] BET surface area=approximately 27 m.sup.2/g.

SRCC01

[0367] The surface-reacted calcium carbonate was produced according to the defined process of the present invention and has the following characteristics:

[0368] d.sub.90=approximately 4.0 μm;

[0369] d.sub.90=approximately 6.5 μm;

[0370] BET surface area=approximately 80 m.sup.2/g.

HydroMg01

[0371] The hydromagnesite was produced according to the defined process of the present invention and has the following characteristics:

[0372] d.sub.90=approximately 1.0 μm;

[0373] d.sub.90=approximately 3.0 μm;

[0374] BET surface area=approximately 80 m.sup.2/g.

GCC02

[0375] The Ground natural calcium carbonate (GCC) is of natural origin and was prepared according to grinding methods known to the skilled person and as described in U.S. Pat. Nos. 5,533,678 or 5,873,935 with the use of dispersing agents during the wet grinding process and treated with 1 wt % of an industrial fatty acid mixture of C.sub.18/C.sub.16 in amounts of 40 wt %/60 wt %. Such industrial fatty acid mixtures can vary in their C.sub.18/C.sub.16 amount from about 30 wt %-70 wt %/70 wt %-30 wt %, as well as in their carbon chain length being from C.sub.14 to C.sub.20. The obtained GCC has the following characteristics:

[0376] d.sub.90=approximately 1 μm;

[0377] d.sub.90=approximately 3.0 μm;

[0378] BET surface area=approximately 6.7 m.sup.2/g.

SRCC02

[0379] The surface-reacted calcium carbonate was produced according to the defined process of the present invention and has the following characteristics:

[0380] d.sub.90=approximately 5.3 μm;

[0381] d.sub.90=approximately 16 μm;

[0382] BET surface area=approximately 30 m.sup.2/g.

SRCC03

[0383] The surface-reacted calcium carbonate was produced according to the defined process of the present invention and has the following characteristics:

[0384] d.sub.90=approximately 5.6 μm;

[0385] d.sub.90=approximately 15 μm;

[0386] BET surface area=approximately 66 m.sup.2/g.

SRCC04

[0387] The surface-reacted calcium carbonate was produced according to the defined process of the present invention and has the following characteristics:

[0388] d.sub.90=approximately 3.5 μm;

[0389] d.sub.90=approximately 7.4 μm;

[0390] BET surface area=approximately 100 m.sup.2/g.

HydroMg02

[0391] The hydromagnesite was produced according to the defined process of the present invention and has the following characteristics:

[0392] d.sub.90=approximately 3.2 μm;

[0393] d.sub.90=approximately 5.0 μm;

[0394] BET surface area=approximately 92 m.sup.2/g.

[0395] The above examples (Table 1 and Table 2) are prepared by previously mixing the above components using a hot/cold mixing process known to the skilled person, and extruding the mixture on a Göttfert extrusion line equipped with a Krauss-Maffei plastifiction unit, L/D 32, with counter rotating parallel twin screws, the screws having a diameter of 30 mm each.

[0396] Properties of the Comparative Examples C1/D1 and C2/D2 and the Inventive Examples E1 to E3, F1 and F2 are shown in the following Tables 3 and 4:

TABLE-US-00003 TABLE 3 Example C1 C2 E1 E2 E3 Density [g/cm.sup.3] 0.78 0.78 0.78 0.74 0.74 Bubble count 1315 1261 1349 1374 1729 Median Bubble 349 331 330 339 307 Circumference [μm] Melt temperature 193.3 192.4 193.7 194.3 194.3 Torque [Nm] 455 416 435 509 468

TABLE-US-00004 TABLE 4 Example D1 D2 F1 F2 Density [g/cm.sup.3] 0.76 0.75 0.67 0.67 Bubble count 1453 1712 1200 1391 Median Bubble 310 280 329 297 Circumference [μm] Melt temperature 191.5 193.8 193.1 194.7 Torque [Nm] 452 441 493 515

[0397] Material densities of the unfoamed material can be calculated based on the density and ratio of the single components. Since all mineral materials have the same density and the formulation remains largely unchanged the “start density” or unfoamed density is given as follows in Tables 5 and 6:

TABLE-US-00005 TABLE 5 Example C1 C2 E1 E2 E3 Density unfoamed [g/cm.sup.3] 1.48 1.35 1.36 1.48 1.48 Density [g/cm.sup.3] 0.78 0.78 0.78 0.74 0.74

TABLE-US-00006 TABLE 6 Example D1 D2 F1 F2 Density unfoamed [g/cm.sup.3] 1.48 1.48 1.48 1.48 Density [g/cm.sup.3] 0.76 0.75 0.67 0.67

[0398] E1 containing only the surface-reacted calcium carbonate of the present invention provides the same density in foamed condition despite having a 0.75 % higher start density due to mineral addition compared to control sample C2. In combination as described in formulation E2 with 25 phr filler composition according to the present invention comprising GCC as second filler and surface-reacted calcium carbonate as first filler the density reduction is 5% despite having a 9.6% higher start density. The use of PCC as second filler described in formulation E3 has a similar effect.

[0399] The following examples (Table 7 and Table 8) are prepared by previously mixing the components listed in the Table 7 and Table 8, respectively, using a hot/cold mixing process known to the skilled person, and extruding the mixture on a Göttfert extrusion line equipped with a Krauss-Maffei plastifiction unit, L/D 32, with counter rotating parallel twin screws, the screws having a diameter of 30 mm each.

[0400] The properties of the products of the Examples are shown in the following in the Table 7 and Table 8, respectively:

TABLE-US-00007 TABLE 7 Effect on Amounts Example A1 A2 A3 B1 B2 B3 Avg. Density [g/cm.sup.3] 0.72 0.74 0.74 0.69 0.65 0.60 Pore count, avg. [—] 1403 1321 1385 1393 1270 1254 Median Pore 328 337 331 320 308 295 circumference, avg. [μm] Tm2 [° C.] 192.7 193.5 194.2 192.9 194.9 196.09 Torque [Nm] 446 461 472 452 503 608 Vynova S6030 (phr) 100 100 100 100 100 100 Baeropan R9347 PS/7 3.5 3.5 3.5 3.5 3.5 3.5 (phr) Plastistrength 566 (phr) 7 7 7 7 7 7 Baerolube PA Spezial 0.05 0.05 0.05 0.05 0.05 0.05 (phr) Genitron EPE (phr) 0.35 0.35 0.35 0.35 0.35 0.35 Genitron TP BCH 51051 0.35 0.35 0.35 0.35 0.35 0.35 (phr) GCC02 (phr) 9 8 7 22.5 20 17.5 SRCC03 (phr) 1 2 3 2.5 5 7.5 Total amount of filler (phr) 10 10 10 25 25 25 Ratio amount GCCC02 to 9 4 2 9 4 2 amount SRCC03

TABLE-US-00008 TABLE 8 Surface area differences Example A0 B2 R1 O1 H1 Avg. Density [g/cm.sup.3] 0.82 0.67 0.64 0.68 0.70 Tm2 [° C.] 197.0 198.0 198.0 196.8 197.7 Torque [Nm] 389 466.3978027 423.8528992 422.404248 431.7584991 Vynova S6030 (phr) 100 100 100 100 100 Baeropan R9347 PS/7 3.5 3.5 3.5 3.5 3.5 (phr) Plastistrength 566 (phr) 7 7 7 7 7 Baerolube PA Spezial 0.05 0.05 0.05 0.05 0.05 (phr) Genitron EPE (phr) 0.35 0.35 0.35 0.35 0.35 Genitron TP BCH 51051 0.35 0.35 0.35 0.35 0.35 (phr) GCC02 (phr) 25 19.6 22 10.7 21.3 SRCC03 (phr) 0 5.4 0 0 0 SRCC04 (phr) 0 0 3 0 0 SRCC02 (phr) 0 0 0 14.3 0 HydroMg02 (phr) 3.7 Total amount of filler 25 25 25 25 25 (phr)

[0401] Consequently, a composition for preparing foamed PVC polymer products comprising the inventive filler composition has been shown to be highly efficient in the maintaining or reduction of foam density. To some extent also a lower median bubble circumference can be provided at the same time.